Dunno what the key looks like for the E38, but these E39 links may provide useful hints for replacing the key body if yours is similar:

The e38/e39/e46/e53 are all generational siblings so things like "keys" are basically the same style. And if there are other models that were being produced during the 1995-2006 era that was from another generation (like the e36 & Z4) and used the same communication bus and keys...all of the info you posted will apply.